JPH07233762A - Exhaust reflux control device - Google Patents

Abstract

PURPOSE:To maintain the function of a valve by directly cooling the stepping motor section of the flow rate control valve with its structure simplified. CONSTITUTION:The device is provided with a flow rate control valve which controls valve opening through motion conversion means 2A and 5A converting the rotating motion of a rotor 24 into a linear motion wherein a stepping motor section 2 and a valve function section 3 are directly connected with each other by housings 2A and 3A for both of them. The aforesaid motor housing 2A is made of material high in thermal conductivity, and is provided with cooling water passages 4A and 4B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust gas recirculation control device, and more particularly to an exhaust gas recirculation control device having an electronically controlled flow control valve whose valve opening degree is controlled by supplying a control signal to a stepping motor.

[0002]

2. Description of the Related Art Nitrogen oxides (NO _x ) contained in exhaust gas of a vehicle engine are generated in a larger amount as the combustion gas temperature is higher and the oxygen concentration remaining after combustion is higher. When such NO _x is released into the atmosphere, it causes the generation of harmful substances due to photochemical reaction. Therefore, in order to suppress the NO _x and to keep the fuel consumption and drivability in the optimum state, a part of the exhaust gas is in the operating state of the engine. The exhaust gas recirculation (EG
R) control devices have been widely adopted so far.

FIG. 3 shows an example of a conventional electronically controlled flow control valve used in such an EGR control device, and this example is of a form disclosed in Japanese Utility Model Laid-Open No. 3-118373. Here, 21 is a stepping motor part, 22 is its motor housing, 23 is an exciting coil,
Reference numeral 24 denotes a rotor rotatably supported by the motor housing 22 via a bearing 25, and 24 A denotes the rotor 2
4 is a female screw portion engraved on the inner peripheral portion. The female screw portion 24A is screwed into the male screw portion 26A of the motion converting shaft 26, and is rotated or rotated only in accordance with a control signal input to the stepping motor 21.
In this example, the motion conversion shaft 26 can be linearly moved upward in accordance with the above operation.

Reference numeral 27 is a transmission member fixed to the end of the motion converting shaft 26 for transmitting the linear motion of the motion converting shaft 26 to the valve shaft 28 side, and 29 is a valve element attached to the valve shaft 28. Also,
Reference numeral 30 denotes a first spring that biases the valve element 29 toward the valve seat 31 via the valve shaft 28, and 32 denotes the valve shaft 28 side and the transmission member 2.
The second spring is interposed between the second spring and the second spring and functions in the same manner. Three
Reference numeral 3 denotes a valve housing in which the valve shaft 28 and valve body 29 are incorporated, 35 denotes a recirculation passage (EGR passage) through which exhaust gas is guided from the exhaust system, 36 denotes a gas return passage for returning exhaust gas to the intake system, and 37 Is the valve housing 3 of the valve shaft 28
3 is a seal member provided around the penetrating portion.

Further, in this example, in order to prevent the high heat due to the high temperature gas from being transmitted from the valve function portion 38 side constituted by the elements assembled in the above-mentioned valve housing 33 to the stepping motor 21 side, the motor A cooling jacket portion 39 is interposed between the housing 22 and the valve housing 33, and the engine cooling water is guided to a cooling water passage 40 of the jacket portion 39.

[0006]

However, in the above-mentioned conventional example, the motor housing 22 of the stepping motor portion 21 and the valve housing 33 of the valve function portion 38 are integrally formed via the cooling water jacket portion 39. However, since the stepping motor section 21 itself has self-heating, and the stepping motor section 21 is often used with a member formed of a resin-based material, the stepping motor section 21 is easily affected by the temperature of the use atmosphere and the temperature due to self-heating. . Therefore, when the control is performed in a high temperature atmosphere even if the heat transmitted from the valve function portion 38 side to the stepping motor portion 21 side is suppressed by the engine cooling water that circulates the corner cooling water jacket 39, Since the motor torque is reduced and the pressing force of the valve element 29 and the spring force of the springs 30 and 32 cannot be fully resisted, there is a risk of malfunction.

Further, not only the life of the stepping motor itself is shortened due to the influence of the above-mentioned high temperature atmosphere and self-heating, but also
Since the number of component parts is large and the structure is complicated, the production cost is high.

An object of the present invention is to simplify the structure in order to solve the above-mentioned conventional problems, and to protect the function of the valve function portion by directly cooling the stepping motor portion of the flow control valve. An object of the present invention is to provide an exhaust gas recirculation control device that can do the above.

[0009]

In order to achieve the above object, the present invention is directed to a stepping motor portion and a valve function portion which are directly connected to each other through both housings, and a rotational movement of a rotor of the stepping motor portion. A flow rate control valve having a motion conversion means for converting the rotor into a linear motion in the axial direction of the rotor, and controlling the valve opening degree of the valve function section through the motion conversion means to control the recirculation amount of exhaust gas. The stepping motor portion housing is made of a material having high thermal conductivity, and a cooling water passage for circulating engine cooling water is provided in the housing.

[0010]

According to the present invention, by rotating the rotor of the stepping motor portion of the flow control valve, the rotation or rotation of the rotor is converted into the linear motion for opening and closing the valve body of the valve function portion through the motion converting means. The valve opening is controlled to control the exhaust gas recirculation amount, but the engine cooling water is circulated in the cooling water passage provided in the housing of the stepping motor section, so it is easy to self-heat and in a high temperature atmosphere. Since the temperature easily rises, the torque of the stepping motor is likely to decrease and the heat is easily transferred.For example, the housing is made of a material with a high thermal conductivity, such as aluminum, and is efficiently cooled by the cooling water. It is possible to prevent the opening / closing function from being impaired.

[0011]

Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 shows a structural example of an electronically controlled flow control valve 1 according to the present invention. Here, 2 is a stepping motor unit, and 3 is a valve function unit. In this example, the motor housing 2A of the stepping motor unit 2 is made of a metal material, such as an aluminum alloy, which has a good heat transfer coefficient, corrosion resistance, and light weight. 4A is such a motor housing 2A
A cooling water passage formed integrally with this along the periphery of the
4B is a cooling water intake for circulating a part of the engine cooling water to the cooling water passage 4A. The cooling water circulating in the cooling water passage 4A removes heat from the motor housing 2A and then returns to a cooling water not shown. It is returned to the cooling passage on the engine side via the passage.

As for the cooling water temperature, in the case of an example for an ordinary vehicle engine, the temperature of the cooling water is delivered at about 30 ° C to 40 ° C by being cooled by a radiator, and at about 80 ° C at most even after the engine is cooled. It is set to be returned to the radiator. Therefore, it can be considered that the cooling water used in this example is also kept at a temperature within the range, and the stepping motor unit 2 can be sufficiently cooled through the motor housing 2A.

Reference numeral 5 denotes a valve drive shaft. In the case of this example, a male screw portion 5A is provided on the valve drive shaft 5 so that it also functions as a motion conversion shaft.

Reference numeral 6 is a spring receiving member fixed to the intermediate portion of the valve drive shaft 5, 7 is a return spring interposed between the spring receiving member 6 and the spring receiving portion of the motor housing 2A, and 8 is press-fitted into the motor housing 2A. Is a bearing member that slidably supports the valve drive shaft 5 and fixes the inner race of the rotor lower bearing 25. It should be noted that, by keeping the above-described male screw portion 5 of the valve drive shaft 5 screwed into the female screw portion 24A of the rotor 24, the rotation or rotation of the rotor 24 is converted into a vertical motion of the valve drive shaft. Can be made. 9
Is a heat insulating sheet provided between the motor housing 2A and the valve housing 3A, and 10 is a sealing device provided to prevent exhaust gas from leaking from the valve function part 3 side to the motor housing 2A side.

FIG. 2 is a system diagram of an exhaust gas recirculation control device incorporating the above-described flow rate control valve 1 relating to exhaust gas recirculation. Reference numeral 11 denotes a control unit for controlling the recirculation amount of exhaust gas, and the control unit 11 has data relating to the relationship between the engine speed and the load, engine cooling water temperature, intake air amount, etc. from the engine 12 side. A program for inputting and controlling the EGR amount according to these data is incorporated, and the stepping motor unit 2 is driven according to the program to control the valve opening degree in the valve function unit 3. Reference numeral 13 is an intake passage to the engine 12, 14 is an exhaust passage of the engine 12, 15 is an exhaust gas recirculation passage, and 16 is an exhaust gas return passage to the intake system. In this example, the gas return passage 16 opens into the intake passage 13 on the downstream side of the throttle valve 17. Also, the engine 12
Part of the cooling water that circulates in the water jacket 12A is supplied to the motor housing 2A as shown by the solid arrow in this figure.

In the exhaust gas recirculation control device constructed as described above, as described above, the rotor 24 is rotationally driven by the stepping motor section 2 of the flow control valve 1 in accordance with the output signal from the control unit 11. The rotational movement is converted into the linear movement of the valve drive shaft 5, so that the valve body 29 resists the spring force of the return spring 7 and obtains the valve opening degree corresponding to the output signal. Is pulled up from. Thus, the exhaust gas guided from the exhaust passage 14 is returned to the intake system side via the gas return passage 16,
It can be mixed in new intake air and involved in re-combustion in the engine 12.

Further, even during the exhaust gas recirculation operation, the stepping motor section 2 is constantly cooled by the engine cooling water through the motor housing 2A of the flow control valve 1, so that the torque of the stepping motor is stabilized even in a high temperature atmosphere. It is possible to prolong life.

[0019]

As described above, according to the present invention, the stepping motor section and the valve function section are directly connected to each other through both housings, and the rotational movement of the rotor of the stepping motor section is controlled by the rotor. A flow rate control valve for controlling the valve opening degree of the valve function section through the motion converting means and converting the exhaust gas recirculation amount through the motion converting means. Since the housing of the stepping motor part is made of a material having a high thermal conductivity and the housing is provided with a cooling water passage for circulating the cooling water of the engine, the temperature of the stepping motor part of the flow rate control valve is kept high in a high temperature atmosphere. It is increased in accordance with the heat generated by itself, and as a result, it is possible to prevent the occurrence of gas leakage due to instability in maintaining the valve closed state due to a decrease in motor torque. , It is possible to enhance the durability. In addition, by diverting the cooling water of the engine, it is possible to keep the stepping motor section at a temperature of at least 80 ° C. or lower. In addition, by providing the cooling water passage in the motor housing, the cooling jacket section is not required, and the flow rate is increased accordingly. The control valve can be made compact. Furthermore, the cost can be reduced by simplifying the structure and reducing the number of parts.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration example of a flow control valve according to the present invention.

FIG. 2 is a system diagram showing an example of an exhaust gas recirculation control device using a flow control valve according to the present invention.

FIG. 3 is a sectional view showing a configuration of a flow control valve according to a conventional example.

[Explanation of symbols]

 1 Flow Control Valve 2 Stepping Motor Section 2A Motor Housing 3 Valve Function Section 3A Valve Housing 4A Cooling Water Passage 4B Cooling Water Inlet 5 Valve Drive Shaft 5A Male Thread Part 6 Spring Receiving Member 7 Return Spring 8 Bearing Member 9 Insulation Sheet 10 Seal Device 11 Control unit 12 Engine 12A Water jacket 13 Intake passage 14 Exhaust passage 15 Exhaust gas recirculation passage 16,36 Gas return passage 24 Rotor 29 Valve body 31 Valve seat 35 Recirculation passage

Claims (2)

[Claims] 1. A step conversion motor section and a valve function section are directly connected via both housings, and a movement conversion means for converting rotational movement of a rotor of the stepping motor section into linear movement in the axial direction of the rotor. The stepping motor part is made of a material having a high thermal conductivity, which has a flow rate control valve for controlling the valve opening of the valve function part through the motion converting means and controlling the exhaust gas recirculation amount. The exhaust gas recirculation control device is characterized in that a cooling water passage for circulating engine cooling water is provided in the housing. 2. The exhaust gas recirculation control device according to claim 1, wherein the housing is made of an aluminum-based material.